This is so not "plugin territory."
A plugin can address the misallocation of link-love on a single site, but the problem is systemic (rather than particular to any individual blog). It's a question of how blogs should interact with one another, and removing nofollow from the core of a hugely popular CMS is an appropriately systemic solution.
Active participation in blogging communities is a perfectly reasonable criteria for assigning stature to blogs. Nofollow is like a cancer treatment, attacking healthy cells in the hope of collaterally damaging some malicious ones. And with the new ubiquity of social media buttons (which generally do not include the nofollow instruction), we're giving all our juice to Facebook and Twitter instead of to one another. (Incidentally, they don't give it back.)
Akismet is a wonderful and effective means of combating spam. Nofollow just harms the sites it's intended to secure. The former largely accomplishes what the latter was intended to do, rendering it unnecessary. WordPress should lead in correcting this web-wide mistake.